package cn.cdcoder.solr.exchange;

import cn.cdcoder.solr.BaseSort;

/**
 * 快速排序
 * @author xusirun
 * @Date 2017/3/21 13:54
 **/
public class QuickSort extends BaseSort {
    public static void main(String[] args)
    {
        int[] a = getData(10);
        // 快速排序
        quickSort(a);
        System.out.println();
        System.out.println("排序之后：");
        for (int i = 0; i < a.length; i++)
        {
            System.out.print(a[i] + " ");
        }
    }

    private static void quickSort(int[] a)
    {
        if (a.length > 0)
        {
            quickSort(a, 0, a.length - 1);
        }
    }

    private static void quickSort(int[] a, int low, int high)
    {
        if (low < high)
        { // 如果不加这个判断递归会无法退出导致堆栈溢出异常
            int middle = getMiddle(a, low, high);
            quickSort(a, 0, middle - 1);
            quickSort(a, middle + 1, high);
        }
    }

    private static int getMiddle(int[] a, int low, int high)
    {
        int temp = a[low];// 基准元素
        while (low < high)
        {
            // 找到比基准元素小的元素位置
            while (low < high && a[high] >= temp)
            {
                high--;
            }
            a[low] = a[high];
            while (low < high && a[low] <= temp)
            {
                low++;
            }
            a[high] = a[low];
        }
        a[low] = temp;
        return low;
    }
}
